| radioactive isotope | <physics, radiobiology> An isotope of an element that has an unstable nucleus, it tries to stabilise itself by giving off ionising radiation. (09 Oct 1997) |
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| stable isotope | A nonradioactive nuclide; an isotope that shows no tendency to undergo radioactive decomposition. (05 Mar 2000) |
| daughter isotope | An element produced by radioactive decay of another. See: radionuclide generator, cow. (05 Mar 2000) |
| isotope | <radiobiology> One of several nuclides having the same number of protons in their nuclei and hence having the same atomic number, but differing in the number of neutrons and therefore, in the mass number. Almost identical chemical properties exist between isotopes of a particular element. The use of this term as a synonym for nuclide is to be discouraged. (16 Dec 1997) |
| isotope clearance | The rate at which an isotope is removed (usually by blood flow) from a tissue or organ such as the brain. (05 Mar 2000) |
| isotope labeling | Techniques for labeling a substance with a stable or radioactive isotope. It is not used for articles involving labelled substances unless the methods of labeling are substantively discussed. Tracers that may be labelled include chemical substances, cells, or microorganisms. (12 Dec 1998) |
| abscopal effect | A reaction produced following irradiation but occurring outside the zone of actual radiation absorption. (05 Mar 2000) |
| additive effect | <biochemistry, chemistry> An additive effect is the overall biological effect two chemicals acting together and which is the simple sum of the effects of the chemicals acting independently. Compare: antagonism. (15 Jan 1998) |
| adverse effect | This is an abnormal or harmful effect to an organism caused by exposure to a chemical. It is indicated by some result such as death, a change in food or water consumption, altered body and organ weights, altered enzyme levels, or visible illness. An effect may be classed as adverse if it causes functional or anatomical damage, causes irreversible change in the homeostasis of the organism, or increases the susceptibility of the organism to other chemical or biological stress. A non-adverse effect will usually be reversed when the organism is no longer being exposed to the chemical. (09 Oct 1997) |
| Anrep effect | A small transient positive inotropic effect of abrupt increases of systolic aortic and left ventricular pressures related to recovery from transient subendocardial ischemia (e.g., cold pressor test). (05 Mar 2000) |
| antagonistic effect | This is the consequence of one chemical (or group of chemicals) counteracting the effects of another chemical, the opposing chemicals cancel out each other's effects. (09 Oct 1997) |
| Arias-Stella effect | Focal, unusual, decidual changes in endometrial epithelium, consisting of intraluminal budding, and nuclear enlargement and hyperchromatism with cytoplasmic swelling and vacuolation; may be associated with ectopic or uterine pregnancy. Synonym: Arias-Stella effect, Arias-Stella reaction. (05 Mar 2000) |
| Auger effect | <physics> Transition of an electron in an atom from a discrete electronic level to an ionised continuous level with the same energy. Synonym: autoionisation. (13 Jan 1998) |
| autokinetic effect | In psychology, the apparent drifting about of a small, fixed, spot of light which is being observed in a dark room. (05 Mar 2000) |
| Bernoulli effect | <physics> The decrease in fluid pressure that occurs in converting potential to kinetic energy when motion of the fluid is accelerated, in accordance with Bernoulli's law. Applied in water aspirators, atomisers, and humidifiers in which a gas is accelerated across the end of a narrow, fluid-filled orifice. (05 Mar 2000) |